Purpose : To present a patient with radiation chiasma neuropathy, secondary to radiotherapy of paranasal sinus lymphoma who was referred for evaluation of gradual decrease of vision in both eyes

Case report : The patient was a 38-year-old male, with history of right maxillary sinus lymphoma, who underwent surgery, chemotherapy and radiation therapy. One year after radiotherapy, he noticed gradual decrease in his right eye vision. He referred to our center 6 months after onset of visual symptoms (1.5 years after radiotherapy). On his first examination, visual acuity (VA) of right eye was no light perception (NLP), and right optic disc was severely atrophic. Other examinations of right eye were unremarkable. The VA of left eye was 10/10 with correction, color vision was normal, slit lamp exam and tonometry was normal as well, but bow tie atrophy of left optic disc was detected. Visual field of left eye revealed temporal hemianopia. MRI showed thickening and enhancement of optic chiasm, especially in right side. In follow-up the enhanced lesion enlarged posteriorly and involved both optic tracts and optic radiations. In spite of treatment with high dose corticosteroid and hyperbaric oxygen, within two years following radiotherapy, vision of left eye gradually decreased to NLP too.

Conclusion : Radiation-induced optic neuropathy is an important differential diagnosis of decreased vision in a case with history of head and neck radiotherapy. Since this complication is very important with ominous consequence, ophthalmologists and radiotherapists should be aware of that and decrease the chance of its occurrence by lowering the dosage, daily fractionation, stereotactic methods, and precise aiming of radiation beam.